In Swift, how to ivalidate NSTimer in AppDelegate on app startup?

I need to translate an iOS app from obj-c to swift. I have NStimer

a ViewController

one that downloads metadata from shoutcast every 30 seconds, but when the app cancels the action, it stops, when it enters the foreground, it starts up again.

Edit: OK. The problem is solved! I added two observers to viewDidLoad named UIApplicationWillResignActiveNotification

and UIApplicationWillEnterForegroundNotification

as shown below:

override func viewDidLoad() {
    NSLog("System Version is \(UIDevice.currentDevice().systemVersion)");
    super.viewDidLoad()
    self.runTimer()
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "invalidateTimer", name: UIApplicationWillResignActiveNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "runTimer", name: UIApplicationWillEnterForegroundNotification, object: nil)
}

      

        
        
        
      

    

and I did two functions. The first is for the start timer:

func runTimer(){
    loadMetadata()
    myTimer.invalidate()
    NSLog("timer run");
    myTimer = NSTimer.scheduledTimerWithTimeInterval(30.0, target: self, selector: "loadMetadata", userInfo: nil, repeats: true)
    let mainLoop = NSRunLoop.mainRunLoop()
    mainLoop.addTimer(myTimer, forMode: NSDefaultRunLoopMode)
}

      

        
        
        
      

    

and the second one to stop it:

func invalidateTimer(){
    myTimer.invalidate()
    NSLog("timer invalidated %u", myTimer);
}

      

        
        
        
      

    

Hope this helps someone. :)